Pipe ramming is a method known in the art which is used to install steel casing pipe for various underground utilities including water, sewer, electric, communications and natural gas facilities. The primary advantage of pipe ramming is that it does not require a trench to be cut in the ground the entire length of the pipe casing being laid. Thus, pipe ramming is commonly utilized to install pipe underneath surface impediments such as highways, railroads, rivers or other structures that prohibit standard excavation and other “cut and cover” pipe laying techniques.
In order to install casing via pipe ramming, a launching and a receiving pit must be excavated on either side of the surface impediment that would prohibit standard excavation and pipe laying techniques. Typically, a pneumatic piston, or ram, is affixed to the back edge of the casing and seated in heavy steel collar that engages with and inside the casing. The ram drives the casing horizontally, or substantially horizontally, forward when the air supply to the ram is actuated.
The leading edge of the casing must be reinforced to withstand the impact as it advances horizontally through the ground. It is also critical to ensure that the outer diameter of the leading edge is slightly larger than the outer diameter of the pipe casing in order to reduce friction as the pipe casing progresses through the soil. A larger outer diameter is traditionally accomplished by welding an external steel ring to the casing. It is equally important that the inner diameter of the leading edge is slightly smaller than the inner diameter of the casing to decrease internal friction of the soil that compacts inside the pipe casing. A smaller inner diameter is accomplished by welding an internal ring to the casing. The installation of these rings in traditional pipe ramming is labor intensive and therefore very costly. The leading edge and inner and outer rings may be referred to as the ramming or thumper head.
A lubricant or cutting/drilling fluid, typically a bentonite slurry, is injected into the annular space created between the outside of the pipe and the soil, as the pipe is being driven. The lubricant is pumped to an external manifold that diverts the slurry through a small opening into the casing and through ports that deliver the slurry to the casing exterior. The manifold is welded to the casing proximate to the leading edge, supplied through a small diameter steel pipe, typically ½″ or ¾″, which is also welded to the casing exterior.
The most efficient way to remove the compacted soil plug from the casing is to “pig” it. Pigging typically involves inserting one or two foamed polystyrene cylinders (the “pigs”) into the pipe casing, and then pneumatically propelling the cylinders through the pipe via a manifold. This ejects the soil plug out of the casing and into an open pit. In a conventional pipe ramming process the head of the pipe casing which includes the leading edge and the outer and inner rings must be cut off before pigging so that the pigs can pass by the internal ring without incurring damage. The casings are frequently difficult to pig because the lubricant is not dispersed uniformly around the internal soil plug, if at all.
After a traditional ramming head is fabricated and used once, it is commonly reused by cutting a short section of about 4′-5′ from the main body of the casing. This short section, including the ramming head, can then be re-welded to a new pipe casing to once again perform the aforementioned function. However, both the initial fabrication and subsequent cutting and welding of the thumper head, is expensive and labor intensive. For example, the welding of a typical 30″ diameter ramming head can take as much as an hour and a half for a two person team to complete.
Thus, what is needed is an easily detachable and reusable ramming head to reduce the cost and increase the speed and efficiency of pipe ramming operations. Furthermore, what is needed is a pipe-ramming head which enables an efficient dispersal and distribution of lubrication for faster and more efficient installation and pigging processes.